Injuries to the anterior cruciate ligament (ACL) are occurring at epidemic proportions especially those resulting from athletic endeavors. The most common surgical treatment for a disrupted ACL is in autogenous bone-patella tendon-bone reconstruction (RACL). The rehabilitation after a reconstruction remains an enigma because of the lack of information necessary to develop universally accepted techniques which are effective and safe. An arthroscopically assisted bone-patellar tendon-bone intra-articular reconstruction of the ACL will be performed utilizing standard graft placement, tensioning, and fixation techniques. At the completion of the reconstruction the investigators will arthroscopically insert into the RACL the Hall strain sensor. The RACL strain pattern will be measured during activities common to physical examination and prescribed rehabilitation programs. These data will be compared with data previously obtained in vivo from a group of patients with normal anterior cruciate ligaments, and demonstrate our ability to restore normal kinematics to the knee joint at the time of RACL implantation. In addition, this data will provide a basis for knee rehabilitation regimes by establishing the effect that variations in joint position, muscle contractions, and external load applied to the knee have on RACL strain. Following surgery a standardized moderately aggressive rehabilitation program will be used for all patients. All patients involved in the study will be asked to participate in an arthroscopic reevaluation approximately one year following the initial surgery. During this procedure the RACL will be instrumented with the Hall strain sensor. The test protocol used to evaluate RACL strain at the time of RACL implantation will be repeated. These data will then be compared to that collected at the time of the initial reconstruction. This will provide a quantitative analysis of any RACL changes during the first year of rehabilitation and identify any effect of healing time, and our rehabilitation program has on RACL strain. In these patients additional testing will be performed to measure the RACL strain pattern during the performance of several activities of daily living. These data will be compared with the data previously obtained in vivo from patients with normal anterior cruciate ligaments. These comparisons will demonstrate the ability of our rehabilitation program to restore normal kinematics to the knee joint one year post RACL implantation, and prove the safety or show any damaging effects of our rehabilitation protocol. These data are expected to be extremely useful to those involved in the evaluation, treatment and rehabilitation of ACL injuries by providing an objective characterization of ACL function. By using these experimental methods, others could prove the effectiveness of their own surgical procedures and rehabilitation techniques.